This invention relates to autodiscovery relative to optical network modules and more particularly to optical autodiscovery between two optical or electro-optical modules employed in a network element of an optical transmission network.
In optical transmission equipment, many equipment manufacturers or vendors authenticate card placement in the equipment chassis by electronically monitoring via the overall network manager or element management system (EMS) in the equipment of network element. EMS is software that manages the network element (NE), which software here is what we refer to as network management software in a management and control module (MCM). It is known in such equipment to apply electronic autodiscovery to determine if a module card has been place in the correct slot in the equipment chassis in a network element and/or if the module card is electrically working properly. However, the technique of electronic monitoring does not and cannot provide a guarantee that the optical paths connecting optical module line cards or optical modules, for example, have been properly connected by a technician or operator upon their installation. A typical optical line side network card in an optical transceiver provides for optical signal generation and optical signal reception of optical client signals from an optical transmission link. These optical client signals are generally generated on the line card side of the transmission equipment but can also be generated on the client or customer-connected side of the network element equipment as well. We refer to the optical modules that includes these optical transmitters and optical receivers as a digital line module (DLM) which includes a plurality of optical signal channels each designed to respectively generate or receive an optical client signal where the optical signals are of different wavelengths so that these signals are then combined and decombined, as the case may be, such as via wavelength division multiplexing (WDM). When a set of optical channel signals from a plurality of signal channels are combined, such as via optical multiplexing, we call the resultant WDM signal an optical channel group (OCG).
The lack of the aforementioned optical module connectivity guarantee is a particular problem where an optical module is improperly connected to another optical module port via an optical cable or fiber in network element equipment chassis. For example, the connected optical module may include another OCG that contains channel signals, for example, that are already present in another optical module that has been previously connected or provisioned in the network element equipment. There are many optical connectors and ports on the front of the equipment chassis and it is not uncommon for the technician to incorrectly interconnect an optical cable, which is also referred to in this disclosure as optical patching, between optical modules. Such incorrect optical cabling or patching is not electronically detectable. Such an incorrect optical connection between first and second optical modules may result in incapacitating other provisioned and working optical signal channels through coherent crosstalk, particularly if one or more of the signal wavelengths of the incorrectly first optical module are identical with one of the signal wavelengths already installed or provisioned to the second optical module. If the error is not detected in advance of optical patching of such incorrect optical patching, the ongoing traffic through the second optical module will be corrupted.
What is needed is some way of optical detection signaling, such as optical autodiscovery, to check for proper optical connectivity, or the lack thereof, which would add significant benefit in booting up WDM network element equipment or permit the network to continually operate without impairment when adding a new optical module into equipment chassis at a network element.